The importance of the primary stage of creep in high-performance aircraft design stems from the fact that allowable deformations have to be limited to relatively small values consistent with the static, thermo-aeroelastic and stability and control requirements of high-speed flight.
The results of primary creep tests on three representative aircraft materials (2024-T86 aluminum alloy, 17-7 PH stainless steel and 6A1-4V titanium alloy) are presented. An outline of the test procedure and the instrumentation employed is given.
A method based on Kanter's exponential equation is proposed for predicting primary creep curves. While purely empirical, this technique has indicated good agreement with experimental results.
A comparison is made between 17-7 PH (RH950) stainless steel and 6A1-4V titanium alloy heat treated to 155 ksi, in which the material density is considered. The results indicate that, insofar as creep is concerned, the titanium alloy is superior to the stainless steel alloy.